In the code below, how do I raise the number of fill levels to, say, 4 or 5?
suppressMessages(library(ggmap))
data(crime)
houston.map <- get_map(location = geocode("Houston"),
zoom = 14)
print(ggmap(houston.map, extent = "device", legend = "topleft") +
stat_density2d(data = crime,
aes(x = lon, y = lat, fill = ..level.., alpha = ..level..),
size = 2,
bins = 10,
geom = "polygon") +
guides(alpha = F))